Fine porcelain or chinaware as it is known in the trade is made with kaolin. When combined with oxygen, silicon makes silica which is common to clay. Another essential part of clay is alumina. When silica and alumina are combined with kaolin which is a very fine white clay, "ball" clay is formed from which porcelain can be and is produced. Ball clay fires white and has a fine white enamel-like surface, with the texture quality and hardness of glass. The enamel-like substance disclosed herein is intended for use as a restorative coating for damaged articles having a porcelain enamel-like surface. Such a coating is intended to cover over and invisibilise mended breaks, cracks and depressions, chips or pock marks in the surface of such porcelain or ceramic articles. There will undoubtedly be other uses such as to line subways, coat storage granaries and the like. Hence, the material described as this invention is not to be construed as limited solely to the craft of china mending. Although the composition invented herein is excellent for restoring and finishing articles that should not be refired in a kiln or otherwise heat treated.
A great need exists for a mending and restoring material externally identical or interchangeable with porcelain and similar ceramics such as faience, majolica, soft paste ware, which requires no kiln or firing and which is hardenable thermogenetically, air-drying, and self-curing, and which may be applied with a brush or by hand. Such material is essentially useful for china repair and coating finishes enamel-like in nature, and as a coating material to fashion identical finishes over broken areas of an existing china or porcelain ceramic article. The material hardens without being subjected to high temperatures and may be used with considerable convenience and efficiency to repair or modify ceramics or porcelains decorated by paint otherwise by materials which would normally be destroyed by subjection to high temperatures or re-firing. The material desirably exhibits a small coefficient of expansion, matching that of porcelain. The material composition desirably withstands high temperatures to which a chinalike object may be subjected in use, such as when being cleaned in a dishwasher. Once cured, the material is impervious to hot or cold water, acids, stains, saline solutions and the like.
It is an object of the present invention to provide a material which is capable, without firing, of hardening into a hard enamel-like coating substance.
It is an object of this invention to provide a conveniently hardenable coating compound which is sufficiently strong and exhibits the lustrous or the glazed enamel finish of porcelain, china-ware or ceramics without firing or heat treatment of any kind.
It is another object of this invention to provide a coating compound which hardens to be substantially impervious to water and to changes of temperature.
It is similarly an object of this invention to provide a composition which can be mixed with oil based paints to enable a ceramist or china-mender to simulate and restore the ceramic article he is mending, in such a manner that the chinaware or ceramic surface of the article is restored to perfection and the damage is invisibilised.
It is another object of this invention to provide a coating composition having a low coefficient of expansion similar to that of china-ware.